Add a custom build rule to the generated build system.
There are two main signatures for add_custom_command.
The first signature is for adding a custom command to produce an output:
add_custom_command(OUTPUT output1 [output2 ...]
COMMAND command1 [ARGS] [args1...]
[COMMAND command2 [ARGS] [args2...] ...]
[MAIN_DEPENDENCY depend]
[DEPENDS [depends...]]
[BYPRODUCTS [files...]]
[IMPLICIT_DEPENDS <lang1> depend1
[<lang2> depend2] ...]
[WORKING_DIRECTORY dir]
[COMMENT comment]
[DEPFILE depfile]
[JOB_POOL job_pool]
[VERBATIM] [APPEND] [USES_TERMINAL]
[COMMAND_EXPAND_LISTS])
This defines a command to generate specified OUTPUT file(s). A target created in the same directory (CMakeLists.txt file) that specifies any output of the custom command as a source file is given a rule to generate the file using the command at build time. Do not list the output in more than one independent target that may build in parallel or the two instances of the rule may conflict (instead use the add_custom_target() command to drive the command and make the other targets depend on that one). In makefile terms this creates a new target in the following form:
OUTPUT: MAIN_DEPENDENCY DEPENDS
COMMAND
The options are:
Specify the files the command is expected to produce but whose modification time may or may not be newer than the dependencies. If a byproduct name is a relative path it will be interpreted relative to the build tree directory corresponding to the current source directory. Each byproduct file will be marked with the GENERATED source file property automatically.
Explicit specification of byproducts is supported by the Ninja generator to tell the ninja build tool how to regenerate byproducts when they are missing. It is also useful when other build rules (e.g. custom commands) depend on the byproducts. Ninja requires a build rule for any generated file on which another rule depends even if there are order-only dependencies to ensure the byproducts will be available before their dependents build.
The Makefile Generators will remove BYPRODUCTS and other GENERATED files during make clean.
Specify the command-line(s) to execute at build time. If more than one COMMAND is specified they will be executed in order, but not necessarily composed into a stateful shell or batch script. (To run a full script, use the configure_file() command or the file(GENERATE) command to create it, and then specify a COMMAND to launch it.) The optional ARGS argument is for backward compatibility and will be ignored.
If COMMAND specifies an executable target name (created by the add_executable() command), it will automatically be replaced by the location of the executable created at build time if either of the following is true:
If neither of the above conditions are met, it is assumed that the command name is a program to be found on the PATH at build time.
Arguments to COMMAND may use generator expressions. Use the TARGET_FILE generator expression to refer to the location of a target later in the command line (i.e. as a command argument rather than as the command to execute).
Whenever a target is used as a command to execute or is mentioned in a generator expression as a command argument, a target-level dependency will be added automatically so that the mentioned target will be built before any target using this custom command. However this does NOT add a file-level dependency that would cause the custom command to re-run whenever the executable is recompiled. List target names with the DEPENDS option to add such file-level dependencies.
Specify files on which the command depends. Each argument is converted to a dependency as follows:
If any dependency is an OUTPUT of another custom command in the same directory (CMakeLists.txt file), CMake automatically brings the other custom command into the target in which this command is built. A target-level dependency is added if any dependency is listed as BYPRODUCTS of a target or any of its build events in the same directory to ensure the byproducts will be available.
If DEPENDS is not specified, the command will run whenever the OUTPUT is missing; if the command does not actually create the OUTPUT, the rule will always run.
Arguments to DEPENDS may use generator expressions.
Execute the command with the given current working directory. If it is a relative path it will be interpreted relative to the build tree directory corresponding to the current source directory.
Arguments to WORKING_DIRECTORY may use generator expressions.
The second signature adds a custom command to a target such as a library or executable. This is useful for performing an operation before or after building the target. The command becomes part of the target and will only execute when the target itself is built. If the target is already built, the command will not execute.
add_custom_command(TARGET <target>
PRE_BUILD | PRE_LINK | POST_BUILD
COMMAND command1 [ARGS] [args1...]
[COMMAND command2 [ARGS] [args2...] ...]
[BYPRODUCTS [files...]]
[WORKING_DIRECTORY dir]
[COMMENT comment]
[VERBATIM] [USES_TERMINAL]
[COMMAND_EXPAND_LISTS])
This defines a new command that will be associated with building the specified <target>. The <target> must be defined in the current directory; targets defined in other directories may not be specified.
When the command will happen is determined by which of the following is specified:
Note
Because generator expressions can be used in custom commands, it is possible to define COMMAND lines or whole custom commands which evaluate to empty strings for certain configurations. For Visual Studio 2010 (and newer) generators these command lines or custom commands will be omitted for the specific configuration and no “empty-string-command” will be added.
This allows to add individual build events for every configuration.